Induction of cytochrome P450 2E1 (CYP2E1) by ethanol appears to be one of the central pathways by which ethanol generates a state of oxidative stress. Glutathione (GSH) is critical in preserving the proper cellular redox balance and for its role as a cellular protectant. The goal of the present study was to characterize the GSH homeostasis in human hepatocarcinoma cells (HepG2-E47 cells) that overexpress CYP2E1. Toxicity in the E47 cells was markedly enhanced after GSH depletion by buthionine sulfoximine (BSO) treatment. The antioxidant trolox partially prevented the apoptosis and necrosis, while diallylsulfide, a CYP2E1 inhibitor, was fully protective. Damage to mitochondria appears to play a role in the CYP2E1- and BSO-dependent toxicity. CYP2E1-overexpressing cells showed increases in total GSH levels, GSH synthetic rate and in γ-glutamylcysteine synthetase (GCS) mRNA. This GCS increase was due to transcriptional activation of the GCS gene and could be blocked by certain antioxidants. Activity, protein and mRNA levels for other antioxidants such as catalase, α- and microsomal glutathione transferases were also increased in the E47 cells. Up-regulation of these antioxidant genes may reflect an adaptive mechanism to remove CYP2E1-derived oxidants. These oxidants are diffusable and were able to elevate collagen type I protein in a co-culture system consisting of the E47 cells + rat hepatic stellate cells. Such interactions between CYP2E1, mitochondria and altered GSH homeostasis, and elevation of collagen levels, may play a role in alcohol-induced liver injury.

Keywords:
CYP2E1, Glutathione, Antioxidants, Toxicity, HepG2 cells, Stellate cells, Collagen type I
This content is only available via PDF.
© 2001 National Science Council, ROC and S. Karger AG, Basel
2001
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.